$ { \left[\begin{array}{rr}{4} & {-2} \\ {-1} & {1}\end{array}\right]+\left[\begin{array}{rr}{-2} & {2} \\ {-1} & {-1}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{4}+{-2} & {-2}+{2} \\ {-1}+{-1} & {1}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{2} & {0} \\ {-2} & {0}\end{array}\right]}$